The major aim of this project is to show that a paradigm found by us to differentiate adults with post-traumatic stress disorder (PTSD) from adults who have had similar experiences but have not developed PTSD can be used to enhance the precision of the PTSD diagnosis in children who have been sexually and/or physically abused. A second aim is to show that physiological measures not only index the degree of distress of abused children but can also be used to separate children with internalizing disorders from those with externalizing disorders. Our paradigms will provide evidence of abnormal nervous system sensitivity, inhibition, attenuated or enhanced startle, and generalization of emotional responses. Over a 5-year period, we propose to screen 600 children (aged 7 to 12 years) who have been abused by someone at least 4 years older than themselves, and who have been referred for abuse-related behavioral and emotional problems. The sample will be limited to non-retarded children. For laboratory studies, we will select subtypes with and without PTSD, matched on the basis of similar experiences, sex, age, and race. A history of victimization form will document stressors: duration and frequency of abuse, number of offenders, relation of perpetrator to child, perception of life threat, physical injury, sexual penetration, social class perpetrator, and family interaction.